The present invention is directed to a size composition and method of producing same for application to glass fibers to produce sized glass fibers with improved dispersibility in aqueous solutions. More particularly, the present invention is directed to a sizing composition and method for producing same for producing sized glass fibers having improved water dispersibility for the formation of paper-like sheet material.
Glass fibers have found application in producing paper-like sheet material composed of either 100 percent glass fibers or a combination of glass fibers along with cellulose fibers. One hundred percent glass paper is a high strength paper and is used as air or liquid filtration papers. When glass fibers are used in combination with natural cellulose fibers including all of the various grades of pulp, the glass fibers are usually of a finer fiber diameter that are more like paper making fibers in length and diameter distribution than the usual diameter distribution for glass fibers. The combination of glass fibers with cellulose fibers have generally improved the drainage, wet strength, and dimensional stability of the resultant paper product.
Also glass fibers are being used as a replacement for asbestos fibers, which although being successful as a reinforcement for many types of materials because of their ability to disperse and to provide some entangled network, have recently been associated with various health problems.
The glass fibers differ from natural cellulose fibers or asbestos fibers in that they are more difficult to disperse in water, and they do not fibrillate in the usual paper making sense. The dispersion problem occurs when a slush, an aqueous solution with dispersed fibers, of glass fibers or a combination of glass fibers and cellulose fibers is prepared as a preliminary step to the formation of a wet web. The dispersion problem is caused by several factors including the longer length of the glass fibers, the electrical charges on the fiber, the differing water absorption characteristics, and the presence of textile sizes or finishes on the glass fibers.
Typically to improve dispersibility of the fibers additional chemicals have been employed in synthetic papers, and these chemicals include dispersing agents, or glass fibers have been produced without the use of any additional chemicals. These agents may be anionic, cationic or nonionic depending on the nature of the fiber, and they may be supplied as a finish on the fiber, but are more commonly added separately to the system. The development of a binding agent like the water-dispersible starch binders for glass fibers have improved the dispersion of the glass fibers in water over the previously used chrome or silane type glass fiber binders. Another approach to improving the dispersibility of glass fiber binders is to produce the glass fibers by flame attenuation. This process produces virgin glass fibers having no surface coating.
The glass fibers produced with a water-dispersible starch binder or virgin glass fibers have not proven satisfactory when the glass fibers have a larger fiber diameter than the micro fibers, i.e., a fiber diameter up to around 6.4 microns, because of the inherent poorer dispersibility of the larger diameter glass fibers in aqueous solution. The larger size glass fibers in the form of fiber glass paper would be an excellent replacement for asbestos fiber paper in such applications as backing or tile floor covering such as vinyl floor covering. But the production of such a glass fiber paper requires a slush which is a stable fiber dispersion. The glass fiber dispersion of virgin glass fibers and glass fibers coated with a water dispersible starch binder have not proven satisfactory.
It is an object of the present invention to provide a glass fiber size composition which yields a size glass fiber with superior water dispersibility.
It is a further object of this invention to produce chopped, sized glass fiber strand products which have superior water dispersibility to enable their use in the formation of a slush which is a stable fiber dispersion to form glass fiber paper useful as a backing material for vinyl floor covering.
It is an additional object of the present invention to provide a sized glass fiber having a fiber diameter of greater than around 6.4 microns that have good water dispersibility and can be used in the production of glass fiber paper or synthetic paper containing a combination of glass fibers and cellulose fibers.